Means for the in-flight cooling of the fuel carried by an aircraft

ABSTRACT

Structure for the in-flight cooling of the fuel carried by an aircraft which has a fuel feed pump for supplying fuel to the engine and a return line through which at least part of the fuel is recycled to the suction side of the pump. A heat exchanger is provided through which a coolant flows in thermal contact with the fuel and a fan is operable to accelerate the flow of coolant fluid through the heat exchanger. The fan is driven by a hydraulic motor which is supplied with part at least of the fuel flow passing through the return line.

Toure United States Patent 0 1-,

[5 1 MEANS FOR THE lN-FLIGHT- COOLING "on THE FUEL CARRIED BY-AN AlRCRAFT [75] Inventor: Klber Toure, Paris.France [73] Assignee :Societe Nationale d'Etudeet'de Construction de Moteurs dAviation,

Paris. France [22] Filed: Jan. 29, 1974 [211 App]. No.: 437.645

[30] Foreign Application Priorityi Data Feb. 5. 1973 France 7s.oa9e2- [52] us. Cl 60139.28 miss/39.244151 511 int. Cl. F02: 9/10 Field of Search 244157.117 A. 135 R;

l37/334. 335.336.3138. 339. 340; 417/408. 4171409.?55:l65/39;60l39.i5.39.18 R.

[56] References Cited UNITED STATES PATENTS 2.483.045 9/1949 Harby 60/39.! R X 2.73l.239 1/1956 Andersen 244/57 UX 3.390.528 7/l'968 Howell et al 60/3918 R X 3.779.007 12/1973 Lavash 60/3928 R P ri mdry Examiner-Trygve M. Blix Assistant Examiner-Paul E. Sauberer Attorney. Agent, or Firm-Watson. Cole. Grindle &

Watson i571; nsmncr, St'rueture' for thein fflight eooiing' ofthe fueic'orried by anlaircraftwhich hasa fuel feed pump forl supplyin; fuel to the engine and a return line through which at ieastpartof the fuel is rec'ycledto the suction side of the punrp.:A-heat exchanger is 'provided: through whichacoolant-flowsin thermal contact with the fuel und'a fan is operable toaccelerate the flow of coolant fluid'through the-heat exchanger. The fan is driven by a hydraulicmotor which is supplied with part at least of the fuel flow passing through the return line.

8 Claims, 2 Drawing Figures I .coolingcrneanslofthe aforesaid kindthus comprises a; hydraulic flgrnoton for; driving: the flow-acceleratin g r an sy'au'd-meansfor 'supplying said hydraulic motor [.fwith part .at'least ofl-the fuel flow passing through .the 'retu'rn j a sua e skill na e anw n pp e e-ta ;-range m tis particular]ysignificant because it-exploits.

The present inventionre tes tdm e ans or flight cooling of the.fuel i'carriedby;a rc'raf q mi with i'f. d iivmn; dizzsai l iiastf l the engine and a return linesueh that iunderlcefrtain; gine operating marti n;atxteasrjpan-er-.meme [deliv-l ered by said feedpurnp a rec cledtoth'e'fsuction arallelismj(whichI:was Y not-self-evi'dent) which beside of the pur 'np., l locomeskap'parent whenrithe altitu'de of thefaireraft in- The in-ilight cooling m'e'ansi comprises a heatexcreases. This relationship occurs between thelincrease changer through .whichqai; coolant t flows ;in thermal in thevolumetric flow rate of the airrequired totflow contact with the fuelto be cooled and means operable ,lthrou'gh the exchangerin order to compensate for the to accelerate the flowof coolant fluid through said heat reduction in specificgravity of the air with altitude and exchanger. i l5. the inereas'e in the flowrate of therecyeled fuel due to in calculating the charaeteristics'ofa heat'exchanger thelfactthatfthefeffective,rateof consumptionpof fuel and in determining the parameters which govern its op fi by the enginefd'ininishes"withaltitude; a :1" eration (dimension, shape, materials. nature and veloct ln 'othehwords. the .energy requirements fordriving ity of circulation of thejfluidsinvolved.-pressure losses. the'flow-accelerating means .,which may be}in the form etcetera.). account is generally taken of a certainnumof a fanor, rotor. and the free" energy available (in the ber of criteria or conditions which must be met. such a t form .ofhighpressurefuelwhich isgbeing recycled) to as the heat exchange'efficien'cy. period of operation of meettheserequirements will vary in the same-sense. the heat exchanger. weight and sizeof the exchanger. The aforesaidhydraulic motor is preferably ahydraulic manufacturing andoperating costs. etcetera. The final turbine.for example a fPelton." turbine. a 1:. choice is therefore normally a compromise between y The floweaccelerating means andthe; hydraulicturthese various conditionswhichare often in conflict; in 'bine' preferablyfcomprise one and thefsanieqrotor the case of a heat exchanger'designedfor installation equipped .with two radially sp'acedarrays of-bladesnein an aircraft. two of the aforesaid criteria are particuspectively traverseclby the cooling fluidand bylthe fuel larly important. namelythe size and the weight of the flowing fromthe return line. Means maygbegprovided heat exchanger which must both be. reduced to, the to regulate the fuel supplied to thehydraulicmotor or greatest possible extent. The fluid utilised for cooling turbineas a. functionof the temperatureof'ithe fuel 'n an1. economical-and advantageous manner. acertain the fuel may be air or oil. y w a being cooled. a 1

in the case of a pump whose delivery "rate is depen- The invention will now be described bylway ofexamdent on the pump operating speed (a gear pump for expie with reference to oneiembodimentof in-flight coolample). the delivery rate required for operation'of the ing means for the fuelof an aircraft which is illustrated engine is achieved by variation of the amount-of fuel in the accompanying drawings. in} which: recycled as controlled byythe engine fuel control-sys- FlG. lis aschematic view of the cooling means,-and tem. One of the effectsof recycling the fuel is to raise FIG. 2 is a schematic view of certain parts of said the temperature of the fuel. However. at highaltitudes. cooling means. e such recycling is very important because .the fuel flow 7 illFiGyl the referencel-signifies an engine such as rate to the injectors. which'is' necessary for the operaa turbojetengine.installed'inan aircraft (not shown) tion of the engine. has to be reduced. The result is a for. propulsion purposes The engine-l. comprises at substantial increase in the fuel temperature-which is leastone burner 2 supplied with fuel from afuel tank added to the temperature rise brought about by the re- Rinstalledin-the aircraft. The tank R is connected to duction in the specific mass of theairjtsothat.' for a, theburner,2 by'meansofa low-pressure line 3, a fuel given heat exchanger. the air cooling efficiency is much pump4 and a high-pressure line 5. The' latter line conless at high altitudes than it is at low altitudesi e tains athrottle and metering device 6.which. depending Thus. if it is required to retain anacceptable aircool- .upon the fuel1requirements, permitlvariation of the efing efficiency at all altitudes. it-isjnec essary to' design fective fuelflow rateQ. q nj en ine. the heat exchanger for operation"athighgaltitudes. ,The pump 4,is pf the fixedidelivei'y;kind-sothat. for Being thus designed toperform efiicientlytheiri-func a-given speed ofrotationtof the pump. the rate'o f delivtion under the most unfavourable conditions. the fuel VeryofJfuel-is constant; Undercertainengineoperating cooling systems contained on board an aircraft are genconditions.- at least a certain fraction Qi'of theflow deerally of substantial size and weightwhich, as pointed ,livered by; the pump 4.must therefore bee-recycled to the sitctionsideof'thepump; .:Accordingly. s 'd-fractionQ, issupplied 'through a out above. is undesirable because of payload and other considerations.

An object of the invention is 'toimprove theeffireturn iin'el7lconimunicating with the tanltl Rby way of ciency of cooling of the fuel carried by the aircraft. The a line 8, which contains a spring-loadedvalve9 serving invention is particularly concerned with the casein also as'an'energy dissipatingdevice. This valve. is open which the cooling fluid. is constituted t by an atmoas soon as the pressure-inthereturn line:7 exceeds a spheric air flow. and has as an object'the reduction at givenlevel and enables-the recycled fuel fraction Q, to least in part of the drawbacksof size and weight hereinreturn. after its'energy has beendissipated. to the reserbefore referred to, by controlling the volumetric-flow .voirgk lnoperation.thecondition Q =.Q, Q, always rate of the air cooling the fuel in order to compensate holds.-This"means that if the effective rate ofwconsumpfor variations in the specific. gravityof the air with altitionQ; of;the.,en'g'ine'isreduced (andthisis particularly tude. Another object is toincrease the overall effi= thecaseas the aircraft'faltitude increases),the.recycled ciency of the aircraft. t flow rateQ,increases.'

The temperature .ofthe fuel containedjin-the tank R tends to rise during a flight.;flrstly because of-the proxjomity of the heat source constituted bythe engine; l to J the tank arid thelines throughiwhichthe fuellflovvsand secondly because of thejdiss' ipation of energyfromi the recycled fuel. For safety reasons. the fuel must therefore be cooled and the fuel} is therefore placedin' heat exchange relationship with a coolantfluidofappropriate kind. such as air. l t a FIG. 1 illustrates a heat exchanger comprising a The ro'dl 26:61: the pas valve 21 is thus displaced towardsfthelleft' so thatfi-the cross&sectional area of the assage 30 is reduced.- C onsequently."the pressure prevailing in tlie line 35 is reduced and the restrictor 22 is displacedtowardsthe left, i.e., in such a' direction as to increase thejrate of fuel delivery to'the turbine 14. The 1 latter aecelerates so {that the ,volume of cooling airflow delivered by'the'1blower1l3"tothefheatexchanger is increased and-yams the" efficiency ofeooling of the .fuel contained in th fmnkgp A screw' 36;bearing"againstthe capsules 25, is provided for adjustment of the operating threshold of the control system. For example. it is possible to adjust the system sothat. below a certain fuel temperature. the turbine 14 does not receive any drive fluid. The blower 13 then simply windmills under the action of the air- Means are provided to accelerate the flow of cooling fluid through the heat'exchanger tubes 10. As shown in FIG. I the flow-accelerating means comprises.'a fan or blower 13. preferably of the helical centrifugal kind. arranged in the intake fairing 11 and driven by a hydraulic motor l4 such as a Pelton" hydraulic turbine. The blower l3 and the turbine 14 have a common rotor journalled in a bearing 40 carried by streamlined arms 41. The rotor has two radially superimposed rings of blades. namely a ring 15 of blower blades and a ring 16 of turbine blades.

The ring 16 of turbine blades rotates inside a casing 17 having an inlet 18 and an outlet 19. The inlet 18 of the turbine casing contains a tangential Pelton" injector and is connected to the fuel return line 7 by a line 20. The outlet 19 of the casing i7 is connected to the" tank R through a line 21. The fluid driving the hydraulic turbine 14 is thus constituted by part at least of the fuel flow O, passing through the return line 7.

The blower 13 is operable to deliver a substantial airflow through the heat exchange tubes 10. The speed of rotation of the hydraulic turbine 14 (and. consequently. the airflow rate delivered by the blower 13) can be regulated by means of a restrictor 22, which thereby permits modification of the flow of highpressure fuel arriving at the turbine. The restrictor 22 can be operated automatically in dependence on the temperature of the fuel in the tank R. this temperature being sensed by a detector 23.

FIG. 2 illustrates an embodiment of the means for controlling operation of the restrictor 22. The detector 23 comprises a hermetically sealed housing 24' immersed in the fuel tank R. The housing contains a set of deformable capsules 25 immersed in an expansible fluid. These capsules are connected. by a rod 26, to a pivot valve 27 arranged for movement within a housing 28 and cooperating with a port 29 formedin said housing in order todeflne a passage 30 of variable crosssectional area. in association with the housing 28, the pilot valve 27 defines a chamber 31 permanently connected to the return line 7 by a line 32.. The chamber 31 likewise communicates. by the variable-section passage 30. a line 33 and a restriction 34, with the fuel tank R. The pressure prevailing in the line 33 upstream of the restriction 34 is tapped through a line 35 and applied to a servo-piston which constitutes the restrictor 22 referred to above.

As the temperature of the fuel in the tank R rises, the volume and pressure of the expansible fluid in the housflow A due to the dynamic pressure consequent upon the aircraft's motion. a

The present invention enables various advantages to be secured. A first of these is constituted by the facility to regulate automatically. as requirements dictate, the efficiency of cooling'ofthe fuel. even though one is using a heat exchanger 10 of reduced'size and weight.

A second advantage resides in theincrease in the general efficiency of the cooling means by the use of the free energy contained'in the recycled fuel flow passing back to the pump 4.

It should be pointedoutthat the exploitation of this free" energy is all the .more timely since it is achieved when the aircraft is flying at very high altitudes. in other words, a favourable'com bination is then obtained between the requirement for increasing the volumetric flow rate of the cooling air inorder to compensate for a the reduction in the specific gravity of the air with increasing altitudes, and a response to this requirement (namely the existence of a larger energy source. constituted by the recycled fuel flow). it should be borne in mind in this context that the effective rate of fuel consumption Q of the engine 1 is reduced as the altitude increases so that the rateof fuel flow Q, available to operate the' turbine is increased and with it the volumetric flow rateof cooling air delivered by the blower 13 to the heat exchanger 10.

in a modified arrangement. the heat exchanger 10. is located outside the tank-R.' to whichit is then connected through fuel flow lines. in addition, thehydraulic motor 14, instead of being located at the periphery of the blower. 13, could be arranged at the blower hub.

I claim: g t

1. Means for the by an aircraft which is equipped with a fuel feed pump for supplying fuel to the engine and a return line so that undercertain engine operating conditionsat least part of the fuel delivered by saidfeed pump can be recycled to the suction side of the ump. said cooling means comprising a heat exchanger through which a coolant flowsin thermal'contact withithe fuel to be cooled,

ing 24 increase. so that the capsules 25 are compressed.

means operable ,to accelerate theflowf of coolant fluid through said heat exchanger. a hydraulic motor for driving said accelerating means and means for supplying saidhydraulic-motor' with at least part of the fuel flow passing through the return line.

2. Cooling means according to claim 1, wherein said hydraulic motor is a hydraulic turbine.

3. Cooling means according' to claim-2, wherein said hydraulic turbine is a Pelton' turbine.

in-flight cooling of the fuel carried- 4. Cooling means according to claim 2, wherein said spaced rings of blades respectively itrayersed,by the cooling fluid and from the fluid flowing from the return line. I J

5. Cooling means accordingto claim I, wherein means are provided for regulating the flow of fuel to 1 said hydraulic motor.

6. Cooling means according to claim 5, wherein means are provided for detecting the temperature of 6 i the fuel andrfor controlling the fuel flow regulating means in dependence on said detected temperature.

7. Cooling means according to claim-l, wherein the cooling fluid is air and-the flowaccelerating means 5 comprisesablower 8: Cooling means-according to claim 6, wherein said \temperature detecting means comprise a chamber contraining an expansible fluid deformable capsules connected to a'pilot yalve.

i l i 

1. Means for the in-flight cooling of the fuel carried by an aircraft which is equipped with a fuel feed pump for supplying fuel to the engine and a return line so that under certain engine operating conditions at least part of the fuel delivered by said feed pump can be recycled to the suction side of the pump, said cooling means comprising a heat exchanger through which a coolant flows in thermal contact with the fuel to be cooled, means operable to accelerate the flow of coolant fluid through said heat exchanger, a hydraulic motor for driving said accelerating means and means for supplying said hydraulic motor with at least part of the fuel flow passing through the return line.
 2. Cooling means according to claim 1, wherein said hydraulic motor is a hydraulic turbine.
 3. Cooling means according to claim 2, wherein said hydraulic turbine is a ''''Pelton'''' turbine.
 4. Cooling means according to claim 2, wherein said flow-accelerating means and said hydraulic turbine comprise one and the same rotor which has two radially spaced rings of blades respectively traversed by the cooling fluid and from the fluid flowing from the return line.
 5. Cooling means according to claim 1, wherein means are provided for regulating the flow of fuel to said hydraulic motor.
 6. Cooling means according to claim 5, wherein means are provided for detecting the temperature of the fuel and for controlling the fuel flow regulating means in dependence on said detected temperature.
 7. Cooling means according to claim 1, wherein the cooling fluid is air and the flow-accelerating means comprises a blower.
 8. Cooling means according to claim 6, wherein said temperature detecting meaNs comprise a chamber containing an expansible fluid and deformable capsules connected to a pilot valve. 